***** mine still stalls on a cold start , worse now even gas pedel doesn't get her alive,once it warmed it has a soild idle with no starting problems??

Dave, I'm worried that the new pot is apparently different from the old. The difference in total resistance is significant, as is the need to find a different setting for idle. The behavior you note could well be due to the differences.

It is reasonable that your idle is steadier - after all the instability is caused because the old pot had an erratic output - the new one is steady. To restore proper operation, though, you will likely have to get the correct pot. Look at it this way - if nothing else, you have diagnosed the idle problem to the airflow meter. If you have to shell out for the MB part and calibrate it, it should solve your problem. Perhaps someone on the board with an 8V or M103/4 will buy your new pot.

Steve

Dave,

I think Steve is right, I bet the trim is incorrectly adjusted or the pot is slightly off alignment. I am amazed that you were able to remove it and install it in the exact same position as the old one given its location and the amount of injection pieces surrounding it. (For those not familiar with the 16V motor, they are a complete bear to work on)

I check the pot number on mine (87 16V) and it is the same number that Steve posted 3437.224.035. I ran the number you posted through a Bosch parts source and nothing came up.

Try to readjust as Steve stated and post your results.

Tinker

the 16v in 87 got a new air flow meter, I have a used 87 one with the 035 pot stock on it , I haven't used it
I measured agian on DC V on 20,
off position
1 and 2 = .01
1 and 3= .00
2 and 3 .00

on position

1 and 2= .07
2 and 3 4.87
1 and 3= 4.85

EHA was -1.17 on position
and running it was -2.11 to - 5.87 at idle
and climbed to + 3.57 around 2500 rpm

do these numbers sound correct or way off??

I got it to start cold by turning the mixture screw a 1/2 turn clockwise ,I leaned it out by doing this ?? correct
Maybe I over my head now but I think I can firgure this out, I don't think it's rocket science, and I really don't like having others work on my 16v,
thanks

Dave,

Are the EHA numbers you posted in ma or DC voltage? All the EHA readings should be in milliamps. The manual states that you should adjust to 0 ma at idle when warm. At a constant 2500 rpm you should not see it fluctuate by more than 10% from the idle reading.

Tinker

No problem...
 

I replaced the pot without a problem.. Took the old one off, set the new one to match.. Put the new one on, and tested the voltage at .63 volts, which seems to be within specs. of +-.25volts..

The new pot seems to work perfectly. I can't honestly say that it solved any problems yet though.. I really couldn't find anything wrong with the one I removed.. Ay 147k miles, it seemed to be in fine shape..

Jay, I'm guessing you still have the idle surging and hot-start problems, since those are what I found in a previous post. Note that in my case, there were other symptoms as well - surging and poor engine braking on decel, and occasional wild swings up to 1500-2200 rpm at idle. None of these have returned since I replaced the pot. In your case too, the car may have spent a greater percentage of its time on the road over the years in motion, instead of idling in rush-hour traffic - which wears that one spot excessively.

There is still a degree of roughness at idle - not silky smooth - that I interpret as injectors with a less-than-perfect spray pattern. This, since I have replaced all the intake hoses and cleaned the idle control valve (and valve job recently too). The actual speed variation is just barely noticeable on the tach, but perhaps this is the idle surge you notice too? I have the correct injector seals on order, and will try my hand at home-brew cleaning and diagnosis of the injectors when they arrive.

If you are getting bigger swings, and have not yet replaced the idle hoses, these harden and form poor contact at connections, allowing air to enter and bypass the airflow meter. When I replaced ours, I also did the rubber lower plenum of the airflow meter - all together pretty inexpensive from FastLane.

Steve

Steve.. With the exception of an intemittent dead skip, which I know is not related, the engine idles so smooth that you wouldn't know it's running.. I replaced it hoping to fix a hot start problem mainly. I have a problem when the engine is warm.. It will start right up, run for a split second, and cut off.. It might do that several times before it will start, and run perfectly..

The old pot.. You would have to look very hard to find any wear at all on the carbon traces..

im curentlly having the same problem as you guys but the cars starts good, my new potentiometer should be here today, i have a 190e 2.3 16v wich are a pain in the a!! to work on but i removed all of the intake system all the way to the intake mainfole butterfly and removed that too and theres a something like the potentiometer on the butterfly i think mine isnt working correctly, i have rough idle and got the car to idle a lot less rough but bow the car lost power, i removed the potentiometer and the black band was very worn, if i didnt put it back on correctly could that be causing the loss of power, i also adjusted the mixture, maybe thats the problem right, anyway im waiting on the new part. also does the 16v have an altitude sensor, and is there a vaccum advance unit on the distibuitor cap like the one i see on the haynes manual for the 8v? i tried adjusting the timing on my 16v by moving the distribiutor cap and nothing happened????:confused:


thanx

DJ,

The switch attached to the butterfly is a throttle position switch. It simply tells the ECU if the car is at wide open throttle or idle. There is an altitude module near the OVP/battery area. If you removed the potentiometer and did not reinstall it exactly as it was removed, then the signal it is sending to the ECU is probably off from the other sensors on the motor. It is not s simple remove and replace. It is difficult to get it perfectly calibrated if you did not mark a reference point before removal. The timing is controlled by the ECU after readings from a speed sensor on the crank pulley. The distributor has no effect on the timing.

Let us know if you having any luck with the new potentiometer.

Tinker

which are the sources for the pot, where did everybody buy it from? and how much?

Page #1... Post #1.. Arrived in about a week..

Jay

ok my AFm number is 0438121022, and my potenciometer part number is 3437224031, wich doesnt match anybodys pot number here'?????? mine is an euro 16v 1985........................

not looking to good DJ, You might be in need parts from europe,
to get a A/F meter or Pot , what does the local dealer in S.Amercia
say about these numbers for your euro 16v?
Dave

sigh..................................

Part Number Concern
 

I just ordered a airflow meter pot for my '88 260e (part no. 3437224035) and now I am having concerns that it is not the correct part. My original pot had 3437224015 on it which supposedly cross references to 035 but when I have not been able to verify that. Has anyone successfully substituted the 035 pot for the 015 or does anyone know of a website that cross references bosch parts. The Bosch site would not recognize either number.

Thanks,

John

Re: Part Number Concern
 

It's the right one.. It's just been slightly re-designed.

Jay

I installed the 035 in my '86 300E. It fit perfectly and I and was able to adjust it to the spec.

Thanks!
 

Thanks Guys,

I should have the new pot next week and we'll see how that goes.

I'm still wondering if it's best to try to adjust the trim pot on the new one to match the old one before installing the pot. I assume you take the resistance readings with the pot out of the car (no wiper contact).

-John

Congratulations ctaylor738,

I have a 260E, 1988, and shows some irregural idle/stalling and I plan to clean the pot.

Could you please indicate (step by step) the procedure you used for adjusting the pot .

it is described in the earier posts... also i have a brand new pot 035 that i bought for a 16v ,that was the wrong one anyone need it
60 bucks shipped
thanks
dave

Here's my contribution to the literature ...
 

http://www.peachparts.com/shopforum/tech-help/72559-300e-airflow-sensor-replacement-old-guys-viagra-post453980.html#post453980

You should note, though, that the crappy idle and stalling showed up again a few days later.

Pot Replacement a Success
 

I replaced the pot in my '88 260e today and the car idles smooth as silk now - no surging or stalling.

Before replacing, I measured the resistance of the old and new pot (pin 1 to 3) and they were 4.07 k ohms and 4.06 k ohms respectively. I also measured the resistance of the trim pot terminals directly, 56.7 ohms old and 56.6 ohms new. Since they were so close, I did not adjust the trim pot.

The replacement pot has the 035 number and the shape of the wiper is a little different from the original 015. The new pot did not come with the rubber perimeter seal so I had to transfer that from the old one.

Aligning the pot on the air flow meter was easier than I thought it would be. I left the mounting screws slightly loose and hooked up a volt meter from the number 2 pin to ground. The car started and ran fine so I rotated the new part clockwise until the voltage dropped way down and the engine died. I turned it back counterclockwise until the voltage got up to about 7.5 volts and the engine surged and died. I ended up setting the alignment at .67 volts (actually it fluctuates between .64 and .69 and called it good.

Thanks everyone for all your help and input.

-John

Thanks John

your description is cristal clear, when I will change my Pot I will use it.

ALIGNING THE POT
 

MR. jOHN PLUT.

CONGRATULATIONS. Excuse me for this stupid question.: Aligning

the pot is done running engine?

Any damage risk rotating the pot with running engine?

Did you get 0.69 V, rotating clockwise from the down end ?


Thanks.


Mario farias
laprefar@cantv.net

Rotating the pot body while the engine is running IS how you make the adjustment. If the engine runs ok when you start it, leave the pot in that position until up to operating temperature, and idle has stabilized. If voltage reading is out-of-range, then make a very small rotation, and wait until idle has restabilized before remeasuring. Repeat until correct.

Steve

Aligning Pot
 

Yes, I aligned the pot with the engine running. I installed the pot using the same alignment marks from the old one and left the screws slightly loose. Then I started the car and and watched the voltage reading (pin 2 to ground) while adjusting the alignment. Be careful to rotate the pot VERY slowly or the engine will surge or die.

Also be aware on the M103 that you have to disconnect the fuel pressure regulator to get at the lower right screw on the pot. I just undid the big fuel connection on the top of the regulator (a small amount of fuel will leak out) and also removed the mounting bolt and pushed the regulator aside enough to get the screw out. My car had T10 Torx screws and a Craftman torx screwdriver worked well to reach through all the wires and hoses. When aligning the pot, you have to hook up the fuel line and then disconnect it again to tighten the lower right screw when completed.

Specs, Where in the WIS they are?
 

Gents,

Trying to find out where in the WIS are the specs to adjust the potentiometer of my 300E and didn't found anything. Can anyone point me to the right page/direction?

TIA,

Mobi

They should all be 0.7 volts. The service manuals were on Braingears.com but that site is now closed. Get a set of manuals, CD's actually, on Ebay or they may be for sale here.

Have it!
 

wbain5280,
Thank you, i have all the WIS CD's/EPC allready installed, could you please be a little bit more specific, which section/number, etc ? BTW, sad to know that braingears is off-line, had many times checked out those webpages when i was away.
Another question, is it 1<->ground, 2<->ground, 3<->ground pins 0.7V? Or between 1<->3, 2<->3 and 1<->2 pins? That's why i need to find the .pdf directly from the WIS, to not disturb the forum and you with questions that i can access myself directly in the WIS-CD's.

Thank you,

Mobi

It is on the CD, but it is buried in one of those tables in the CIS troubleshooting and diagnosis section. Unfortunately, my CD's went with the car.

Finding 3437224015
 

Finding 3437224015 or the new one ending 035?

Hi, does any body know if these available anywhere at the moment?

Thanks, Paul.

I have searched on-line for one recently and was told by everyone that they are no longer available. I think you can still purchase the entire airflow sensor but that is really expensive and much more work.

-John

M119
 

Is the 0.7V the same for the V8? It's the same part.
I have 1.1 volts at idle and it idles fine...but the rpm does surge while driving. Could this still be the pot.?